What St. George water does to a water heater

What the manufacturers wrote

The figures below were taken from the manufacturers' own warranty PDFs and installation manuals.

• Noritz limited warranty, excluded: "Damage as a result of use with non-potable water, untreated or poorly treated well water, or water with high PH levels or hardness levels in excess of 12 grains per gallon (200 mg/L)."
• Rinnai installation manual: "Replacement of components due to water quality damage is not covered by the warranty." And: "If you install this water heater in an area that is known to have hard water or that causes scale build-up, the water must be treated and may require a more frequent flushing schedule."
• Bradford White (tank) warranty, excluded: failure from "sediment or lime precipitate in the glass lined tank," and "maintenance contrary to the written instructions furnished with the unit." Anode removal is listed under misuse, with an express carve-out for "removal of the anode rod (except for inspection and/or replacement)."

How to read those exclusions honestly

Read what kind of clause it is, because they are not all the same. Rheem's is an exclusion on the damage, so a scaled heat exchanger claim is denied while an unrelated control board failure normally is not. Noritz is stronger: its heading says the warranty "becomes null and void." Either way the accurate summary is this: in St. George, an untreated tankless installation is effectively an uninsured heat exchanger. The maker has already written the denial letter.

One maker goes the other way, and it is worth knowing before you choose a unit. A.O. Smith's current limited gas tankless warranty publishes no hardness figure at all. Its water quality exclusions name pH outside 6.5 to 8.5 and iron above 0.3 mg/L, and it says that failure of a heat exchanger due to excessive scale accumulation on units equipped with X3 technology is eligible for warranty coverage for 15 years. That is the opposite of an exclusion. We read the document rather than repeating what circulates about it.

Two more traps sit in the same documents. Rinnai and Rheem both cap total dissolved solids at 500 mg/L. St. George's 2024 water quality report shows TDS from 118 to 936 ppm depending on which source blend feeds your street, so the high end is 1.9 times the limit, a second and independent ground for exclusion. And Rinnai and Rheem both end warranty coverage at 12,000 operating hours regardless of calendar years. A scaled unit runs longer to deliver the same gallon at the same setpoint, so scale runs the hours clock faster too.

Now the part that gets written wrong more than any other. The city's 18 grains is what you tell the softener the incoming water is. It is not the output. Softened water leaving a properly sized and set softener is functionally 0 to 1 grain, which clears every limit in the table. Anyone who says softened water here still measures in the high teens has confused the two numbers.

Salt-free "conditioners" using template-assisted crystallization do not remove calcium or magnesium; total hardness at the tap is unchanged. The manufacturers' limits are written as total hardness, so on our reading a conditioner does not bring an 18 grain house under the 200 mg/L limit. That is our reading, not a manufacturer's ruling; confirm with the maker of your unit. What a conditioner does do is add zero chloride to the sewer, which matters here for a reason below.

What hardness does to any water heater: the Battelle numbers

The Water Quality Research Foundation commissioned Battelle Memorial Institute to measure it. A gas storage heater loses 4 percent efficiency for every 5 grains of hardness; softened water held factory efficiency over a 15-year test life. An electric heater accumulates about 0.4 pounds of scale a year per 5 grains. Showerheads lost 75 percent of their flow in under 18 months, and faucet strainers were nearly plugged after 19 equivalent days. A tankless heater on 26 grain water failed completely after 1.6 years of equivalent use.

Applied to the city's own figure, 18 grains works out to roughly a 14 to 15 percent efficiency loss on a gas tank; at 22 grains, about 17 to 18 percent. The study's tankless failure case was 26 grains, above St. George's stated range. We are not telling you a tankless fails here in 1.6 years. We are telling you the failure case was 26, the city's number is 18 to 22, and the manufacturers wrote their exclusions because the failure is real.

Why your neighbor's heater lasts longer

St. George draws from three kinds of source: springs on Pine Valley Mountain, wells in the Gunlock and Snow Canyon areas, and Virgin River surface water stored in Quail Creek and Sand Hollow and treated at the Quail Creek plant. Within one city the 2024 report shows TDS from 118 to 936 ppm and sulfate from 1.38 to 451 ppm. That is not measurement noise. It is the difference between Navajo Sandstone groundwater and river water that drains gypsum-bearing formations upstream. Your scaling rate depends on which pressure zone serves your street, and it shifts through the year as the city blends sources.

No water quality report in the county publishes hardness; it is not a federally required parameter. A city-wide number is not your number, and a treatment recommendation should come from a test at your tap.

Sulfate has its own effect inside a tank. A standard magnesium anode rod reacts with sulfate-reducing bacteria to make hydrogen sulfide, the rotten-egg smell, and homes on the higher-sulfate blends are more likely to get it. The usual fix is an aluminum-zinc rod. A powered anode, which protects the tank with an external current instead of sacrificing metal, works better as TDS rises. Note the Bradford White line above. Replacing an anode is maintenance and is expressly carved out. Pulling one and leaving it out is listed under misuse.

The advantage St. George has for tankless, and the one objection left

A tankless unit's output depends on how far it has to raise the incoming temperature, and St. George's incoming water is far warmer than northern Utah's. Using a winter inlet near 60°F, a 199,000 BTU condensing unit delivers roughly 6.3 gallons per minute at 120°F; the same unit in a 45°F-inlet market delivers about 5.0. That leaves hard water as the only serious objection, and hard water is solvable: the softener is part of the water heater installation here, not an accessory to it.

What else is in the water

Arsenic is the real local story. St. George's running annual average is 8.68 to 9 parts per billion against a federal limit of 10, with individual samples as high as 13. Ivins and Santa Clara both run dedicated arsenic-removal treatment on their well sources. The water is legally compliant, with little headroom. A softener removes no arsenic. A point-of-use reverse osmosis unit at the kitchen sink does.

Hexavalent chromium is measured at 0.279 ppb in St. George and 1.22 ppb in Hurricane; there is no federal limit for it. The disinfectant is chlorine, not chloramine, which is the oxidant implicated in polybutylene pipe failure in homes built from roughly 1978 through the mid-1990s, and which ordinary activated carbon removes more easily than chloramine.

If you have seen the Environmental Working Group's multipliers for this water, read them with all three columns. EWG's guidelines are its own numbers, far below federal limits. Every system here is in compliance with federal law.

Maintenance at this hardness

Tankless: flush and descale every six months, not annually. Rinnai's manual says hard-water areas "may require a more frequent flushing schedule," and Rinnai units carry a service indicator with selectable intervals of 0.5, 1 or 2 years. In St. George it belongs at 0.5. Most installers leave it at the default. Check yours.

Tank: flush at least once a year; popping and rumbling is scale on the bottom trapping steam. Inspect the anode at three years.

Softener: the city asks residents to keep the setting low because softener salt raises TDS in the reclaimed water used for irrigation. A time-clock softener regenerates whether you used water or not; a demand-initiated one regenerates on measured volume. Set it to the measured hardness at your tap.

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